The present invention relates to automated mail processing systems, and in particular to a method of detecting overlapping mail pieces in a singulated stream of mail pieces.
In conventional mail processing systems, stacks of letters and flats are processed using automated sorting machines including one or more feeders. A problem frequently encountered with mail feeders is double or multiple feeding, i.e. overlapping mail pieces are output by the feeder. When the feeder outputs multiple over lapping mail pieces, the mail pieces cannot be scanned, resulting in mis-sorting and other operational problems. The method and apparatus disclosed herein is designed to detect overlapping mail pieces in a stream of singulated mail piece so that corrective action may be taken.
The invention provides an apparatus and method for detecting overlapped mail pieces when sorting batches of flat mail pieces as the pieces are conveyed on their narrow sides, whereby the sorted mail pieces are moved successively standing on their narrow sides in a longitudinal direction along a bed or path. Positioned below the path is an electronic line camera arranged with its longitudinal axis perpendicular to the feed direction of the sorted mail pieces that scans the lower narrow edges of the mail pieces through a gap in the bed. In one aspect, two sources of light, such as light emitting diodes, are positioned laterally from the line camera diagonally illuminate the mail pieces from below as the mail pieces pass over a window in the path so that the edges of the scanned narrow sides are emphasized by shadowing. Features of the scanned images are transmitted to an evaluation means that utilizes statistical analyses and compared with models of known physical mail piece configurations determined off-line to determine the model that most agrees with the analysis of the scanned image data. In one aspect the evaluation means comprises a microprocessor that is preprogrammed to compare and statistically analyze the captured image data with reference to standard image data and determine the probability that the scanned image data represents over lapping mail pieces, in which case the microprocessor generates a signal that triggers corrective action.
In another aspect, the device the brightness and/or intensities of the scanned lines are determined and selected to be stored and the lines with the same number of intensity maxima are combined into segments, whose differentiating segment features include number of intensity maxima, sequence and features of segments. These segments and features are compared with the appropriate known models and the model with the largest agreement is selected as the recognition result.
In yet another aspect, a method of detecting multiple, overlapping mail pieces in a stream of mail pieces comprises: 1) using a mail piece feeder to successively feed mail pieces on a one by one basis in a singulated stream wherein the mail pieces are conveyed on edge; 2) conveying the mail pieces along a path including a gap or window over which the mail pieces pass on edge; 3) scanning the mail pieces to capture a series of images comprising a linear array of pixels having varying intensities; 4) analyzing the series of linear images to determine whether one or more than one mail piece is passing by the window at the same time; and optionally 5) taking corrective action if a double, multiple or other abnormal feeding condition is detected.